In the prior art, ballast circuits are well known. Most of them are extremely heavy and cumbersome and generate large amounts of heat during operation. Ballasts are used in many lighting applications and their main area of application consists of neon sign applications and fluorescent lighting applications.
Regarding the neon sign applications, neon signs customarily require on the order of up to 15,000 volts to drive the controlling circuit. Thus, neon signs as they are presently made, must be made with quite heavy support structure for high voltage conductors which makes neon signs as they are presently manufactured, extremely cumbersome and difficult to install. Further, the need for high voltages in neon signs drastically increases power usage as well as heat generation and makes such signs, over long periods of time, fire hazards.
Furthermore, the high voltages described above are necessarily a part of the present day magnetic transformers. Thus, a need has developed for an electrical circuit which may be utilized to control the lighting of neon signs which uses low voltage so that the signs do not have to be made with the cumbersome and heavy structure for high voltage conductors. Further, a need has developed for an electrical circuit to control a neon sign in a manner so that the entire sign may be lit uniformly.
In a further aspect, it is well known that in cooler weather, the intensity of known neon signs diminshes and accordingly, a need has developed for an electrical circuit to control a neon sign which may compensate for weather conditions in a manner such that the intensity of the light emanating from a neon sign may be kept uniform regardless of ambient temperature conditions.
Concerning fluorescent lighting applications, it is well known that most ballast circuits which are utilized in fluorescent lighting applications are extremely heavy and large and fill up a great portion of the lighting fixture housing. Since these heavy and cumbersome ballast systems generate a great deal of heat during their operation, in environments such as office buildings where a large number of fluorescent fixtures are used, the heat generated by the ballast circuits is significant enough to have an adverse effect on utility bills as additional air conditioning capacity is required to compensate for the heat generated by the ballast circuits. Furthermore, the extreme weight of these ballast circuits, when combined with the weight of the lighting fixtures themselves, contributes to making the handling of such lighting fixtures, during their installation, extremely difficult.
Thus, a need has developed for a new ballast circuit which will drastically reduce the weight of a lighting fixture including such ballast circuit with the lighter ballast circuit also generating less heat so that buildings having many such lighting fixtures may have cooling systems of less capacity with the resulting lowered utility bills.
In a further aspect, in all lighting applications, a need has developed for ballast circuitry with great versatility allowing the user thereof to control many different lighting applications with a single circuit, while allowing the user to control each particular lighting application in several ways, for example, dimming, flashing, etc.
In a further aspect, it is known that in neon circuits, often bubbles appear within the neon tube which bubbles are not desired. Applicant knows of no circuit which has yet been designed which enables one to control the formation and disappearance of these bubbles and a need has developed for circuitry which will enable one to controllably create and dissipate bubbles within a neon tube.
The following prior art is known to Applicants:
U.S. Patent 3,969,652 to Herzog discloses an electronic ballast circuit for gaseous discharge lamps which includes a time-ratio circuit and inductor which controls the current to the lamp. A closed loop feedback system ties the system together. This circuit is different from the teachings of the present invention since the present invention does not utilize a series switching regulator or TRC to control current to the lamp.
U.S. Patent 4,005,335 to Perper discloses a high frequency power source for fluorescent lamps and the like which comprises a protection circuit for use in "generally conventional invertors with oscillator circuits". The present invention is distinct from the teachings of this patent, mainly because the present invention does not use any protection circuit such as that which is set forth in this patent.
U.S. Patent 4,060,752 to Walker discloses a discharge lamp auxiliary circuit with dI/dt switching control. This patent discloses a high Q resonant circuit which is provided to maintain high output voltage when the lamp is started or re-ignited. Since the present invention does not use any resonant circuit which may be considered to be analogous to the teachings of Walker, this patent is believed to be irrelevant to the teachings of the present invention.
U.S. Patent 4,127,797 to Perper discloses an inverter oscillator with current feedback circuit. This patent discloses, over and above the Perper patent described hereinabove, the addition of a feedback circuit for regulation of the lamp load. Thus, since the present invention does not regulate in the manner contemplated in this patent, this patent is believed to be irrelevant to the teachings of the present invention.
U.S. Patent 4,277,726 to Burke discloses a solid state ballast circuit for rapid start type fluorescent lamps which operates from AC line voltage. This patent discloses a self-oscillating circuit and fails to disclose any control of the set point of inductors and capacitors in the circuit. The present invention utilizes control means which is clearly distinct from the teachings of this patent, as will be described in greater detail hereinbelow.